In a telecommunications system, signals may emanate from a source, e.g., a calling party, and be routed through the system to a sink, e.g., a called party. Between the source and the sink, the signals may be operated upon in a number of ways, usually for improving the efficiency of the system. For example, an analog speech signal may be converted to a digital speech signal, be reconverted, be routed through pulse code modulation (PCM) apparatus, and, perhaps, be routed through time assignment speech interpolation (TASI) apparatus onward ultimately to the sink.
Speech interpolation systems commonly employ speech detectors for detecting a signal on a trunk and classifying the signal among one of a plurality of classifications. A typical speech detector is of the type disclosed in U.S. Pat. No. 4,028,496, entitled "Digital Speech Detector" and issued to R. E. LaMarche et al on June 7, 1977. Although the use of the word "speech" in the phrases "speech detector" and "speech interpolation" may be a misnomer, such use is common in the art. For example, more typically, a speech detector detects energy of a first type and energy of a second type. The first type energy is usually referred to by the generic "energy" while the second type energy is referred to as "noise." Thus, known speech detectors include arrangements for classifying signals between energy and noise.
As mentioned, a common use for speech detectors occurs with systems such as the digital speech interpolation (DSI) system disclosed in U.S. Pat. No. 4,002,841. There a speech detector extends a trunk activity signal (TAS) for indicating whether energy or noise was detected on the trunk. Responsive to the TAS signal, a processor processes a signal on the trunk. For example, if the TAS signal indicates that energy has been detected, the signal on the trunk may be routed toward its sink. The trunk in this instance is said to be "active." On the other hand, if the TAS signal indicates that noise has been detected, the signal on the trunk may not be routed but rather may be disgarded. The trunk in this instance is said to be "inactive." As a result, only signals from active trunks are classified as energy signals for routing through the system.
Also, in the course of routing energy signals through the system, it may be desirable to process different energy signals according to different methodologies. For example, during overload, the DSI system disclosed in the aforementioned U.S. Pat. No. 4,002,841 may truncate bits of the digital signal in an orderly fashion for further improving the efficiency of the system. On the other hand, in arrangements having, for example, a first source computer "talking" to a second sink computer, the source signals may be digital signals and it may be undesirable to truncate bits from the digital signals. Heretofore, telecommunications systems appear to have been peculiarly devoid of apparatus for relatively quickly classifying the routed energy signals as between signals of a first class for processing according to a first methodology, e.g., speech signals, which may have bits truncated, and signals of a second class for processing according to a second methodology, e.g., nonspeech signals, which may not have bits truncated.